1. Field of the Invention
The present invention relates to a metallic gasket such as cylinder-head gaskets and so on made therein with holes such as combustion holes, water holes, oil holes and so on and, more particularly, to a metallic gasket having a metallic sheet in which a recess formed around the hole is charged with an elastic sealing member to ensure sealing a joint between confronting members around the hole.
2. Description of the Prior Art
Conventionally, joints in high-pressure lines have been tightly connected with each other through gaskets interposed between flanges that are formed at pipe ends to be connected, one to each end. Among the gaskets ever used is an O-ring accommodated in recesses made in the mating surfaces of the flanges. Most O-rings have ever been considered and standardized as to design conditions such as the configuration of an O-ring itself, the configuration of a recess, the clearance into which the O-ring extends above the recess, and so on. With the metallic cylinder-head gaskets for engines, moreover, there has been used metallic plates that are provided on surfaces thereof with grooves in which elastic sealant of rubber, resinous material and so on is applied by, for example printing to seal around the holes made in the metallic plates for allowing coolant and the like to flow through there.
Recent trends in the automotive engine development are towards a lowering of the force needed to tighten head bolts, high-pressure combustion in engines, much wider use of aluminum alloys for major engine components, adoption of monolayer gaskets or reduction in number of metallic sheets to be overlaid to form the gasket, and so on. Nevertheless, the optimal design conditions for the cylinder-head gaskets to cope with the trends stated earlier do not yet come to light. Unlike the industrial fields where the O-ring has been ever used, most cylinder-head gaskets in the engine normally experience minor amounts of shrinkage and/or expansion during engine operation at not only areas limited around the water holes but also at other areas neighboring the head bolts tightened.
With the metallic gaskets, the elastic sealing member of rubber, resinous material and so on having the cross section in excess is preferable for ensuring a high statistic sealing stress when being squeezed. However, the excessive elastic sealant causes an occurrence of local bulge of the sealant between the mating surfaces to leave any clearance between the mating surfaces to be jointed tightly and further an occurrence of any strain and flowage of the sealant thereby hindering the elastic sealing member itself from following properly the shrinkage and/or expansion that might happen in the clearance between the mating surfaces of the cylinder head and the cylinder block, so that there is always a certain possibility that a fluid will leak through. Moreover, the elastic sealing member is apt to be much subject to premature degradation and any collapse due to stress loaded repeatedly. In contrast, the elastic sealing member sparse in cross section will have a strong possibility of failing in sealing effect. That is to say, the prior art has uncovered no critical condition to use the elastic sealing member of rubber, resinous material and so on within its elastic characteristic region.
Among prior sealing means around the bolt hole in the metallic gaskets is a monolayer metallic gasket in which there is provided a metallic sheet made with a folded flange around the bolt hole to allow tightening the gasket to the specified torque (refer to for example Japanese Patent Laid-Open No. 200506/1996, and Japanese Patent Application No. 2000-92021, a co-pending senior application of the present applicant). In the metallic gaskets recited just above, either the folded portion or the half bead chiefly provides the sealing construction around the bolt hole.
For example in another co-pending senior Japanese Patent Application No. 2000-83442, there has been also proposed an aluminum gasket provided with identical sealing constructions around the head-bolt holes. Even with the gasket recited earlier, however, there has not been followed any relation of the recess on the metallic sheet with the elastic sealant received in the recess.
Disclosed in, for example Japanese Utility Model Laid-Open No. 30628/1993 is another cylinder-head gasket in which a base sheet of the gasket is made on opposite sides thereof with grooves, one to each side, where printed sealing members are adhered to be raised above their associated sides. When the gasket is squeezed between the mating surfaces of the cylinder head and the cylinder block by tightening head bolts, the printed sealing members are allowed to make deformation to be embedded securely in the grooves on the opposite sides of the base sheet, thereby improving the sealing effect.
Japanese Patent Laid-Open No. 200503/1996 discloses a cylinder-head gasket in which a strip of sealant is equal in width to a groove in the metallic sheet so as to cover the overall bottom surface of the groove recessed below the associated side of the metallic sheet.
Moreover, the cylinder-head gaskets have been ever disclosed, in which the printed sealant is adhered in the groove to extend above the associated side of the base sheet. Nevertheless, such gaskets include only a recitation of any condition to raise the sealant above the side of the metallic sheet and, therefore they do not succeed to utilize well the elastic characteristics of the sealant itself for realizing the sealing means of high sealing reliability.
On the other hand, any multi-layered gasket especially for the engine construction with chain case is needed to provide seals simple in construction, with even high reliability. To cope with this, a three-layered gasket has been proposed as disclosed in, for example Japanese Patent Publication No. 20626/1991 and Japanese Patent Laid-Open No. 119836/1995. The three-layered gasket recited above has still a major problem of how to strengthen the seal on the lower metallic sheet at the chain case.
With the metallic gasket adapted for the cylinder-head gasket that is made therein with various holes such as combustion holes, water holes, oil holes, and bolt holes in which head bolts fit to joint together the cylinder head the cylinder block, it may be worthwhile providing an improved metallic gasket in which an elastic sealing member of rubber, resinous material and so on is placed in a recess or groove formed around the holes to ensure sealing effect around the holes, and in particular the elastic sealing member is kept in a specified relation with the recess or groove in their cross-sectioned configurations so as to utilize an elastic characteristic region inherent in the elastic sealing member itself for realizing the improvement in the sealing effect.
In a metallic gasket adaptable to a cylinder-head gasket interposed between the cylinder head and the cylinder block, a tri-face seal gasket interposed between the cylinder head and the cylinder block with chain case, and so on, a primary object of the present invention is to provide a metallic gasket of either monolayer type or multi-layered type, in which an elastic sealing member is placed in a recess formed around a combustion hole in a metallic sheet, and the elastic sealing member is kept in a specified relation with the recess or groove in their cross-sectioned configurations so as to use the elastic sealing member within an elastic characteristic region inherent in the elastic sealing member itself for realizing the improvement in the sealing effect, with even more inexpensive.
The present invention is concerned with a metallic gasket adapted to be disposed between mating surfaces of engine components, which is composed of a metallic sheet made with a hole and a recess surrounding around the hole, and an elastic sealing member installed in the recess, the improvement characterized in that the recess is defined by a bottom surface and side surfaces merging the bottom surface with any one major side of the metallic sheet; the elastic sealing member, when free of tightening force, is constructed with a bottom covering entirely the bottom surface of the recess and partially the side surfaces of the recess, a top extending above the major side of the metallic sheet, and slopes extending between the top and the bottom; the elastic sealing member is made not more than the recess in a cross section perpendicular to the major side of the metallic sheet; and the elastic sealing member, when tightened, experiences an elastic deformation, a maximum amount of which is limited within an area of the recess.
With the metallic gasket constructed as stated earlier, when it is squeezed between, for example the mating surfaces of the cylinder head and the cylinder block, the elastic sealing member may be used within the range of elastic limit inherent in the elastic sealing member of rubbers, resins and so on. That is to say, a top part of the elastic sealing member extending above any major side of the metallic sheet functions as the corrugated bead, while another part contained in the recess below the major side of the metallic sheet serves as a base to bear the top part. Thus, the deformation occurring in the elastic sealing member, as confined to only the elastic deformation in the area of the recess, does not result in the breakage of the elastic sealing member.
According to one aspect of the present invention, there is provided a metallic gasket in which the hole is at least any one of a combustion hole, a bolt hole in which a tightening bolt is allowed to fit, a water hole for passing cooling water through there, an oil hole allowing engine oil to flow through there, and an opening for a chain chamber in which an endless chain runs.
According to another aspect of the present invention, there is provided a metallic gasket in which the metallic sheet is made of any one of a single metallic plate and a lamination of more than one metallic sheet. When a single metallic sheet is selected, the recess is made on either any one major side or opposite sides of the metallic sheet. In contrast, when a lamination of more than one metallic sheet is adopted, the recess is formed on either any one or both of the outside major sides of the outermost metallic sheets.
According to a further another aspect of the present invention, there is provided a metallic gasket in which the bottom of the elastic sealing member has a height of at most about two-thirds a depth of the recess. In order to ensure the elastic deformation of the elastic sealing member under the squeezed condition with the elastic sealing member being confined within the recess in their cross section, it is preferable that the height where the widthwise far hems of the elastic sealing member reach the side surfaces of the recess is kept at most about two-thirds a depth of the recess.
According to another aspect of the present invention, there is provided a metallic gasket in which a peak of the top of the elastic sealing member is set at a height of a range of from 0.1 to 1.0 mm, preferably a range of from 0.1 to 0.5 mm, above the major side of the metallic sheet. In order to ensure the elastic deformation of the elastic sealing member under the squeezed condition with the elastic sealing member being confined within the recess in their cross section, the height up to the peak above the major side of the metallic sheet, or the height subject to the deformation should be limited to the specified range recited just above.
According to another aspect of the present invention, there is provided a metallic gasket in which the elastic sealing member is made less in cross section than the recess by about from 20 to 25%. This helps ensure the elastic deformation of the elastic sealing member under the squeezed condition with the elastic sealing member being confined within the recess in their cross section. Moreover, the elastic sealing member is made throughout a length thereof less in cross section and also in volume than the recess.
According to another aspect of the present invention, there is provided a metallic gasket in which the side surfaces defining the recess arranged in a manner either flaring out upwards from the bottom surface surface of the recess to the major side of the metallic sheet or extending upright from the bottom surface of the recess to the major side of the metallic sheet.
According to another aspect of the present invention, there is provided a metallic gasket in which the recess is formed on each of opposite major sides of the metallic sheet and the recesses on the opposite major sides are arranged in either aligned or off-set relation with each other across the metallic sheet.
According to a further another aspect of the present invention, there is provided a metallic gasket in which the elastic sealing member is made of at least any one selected from resins, rubbers and adhesive polymers. The elastic sealing member is made of any material that, when squeezed between the mating surfaces, may experience elastic deformation by compressive clamping force applied from the mating surfaces, thereby making tight seals between the mating surfaces.
According to another aspect of the present invention, there is provided a metallic gasket in which the elastic sealing member is adhered to the recess by using at least any one way of printing, adhesion, coating and ink-jetting. Adhesion of the elastic sealing material into the recess makes it possible to provide simply the elastic sealing member, with even steady and inexpensive.
According to another aspect of the present invention, there is provided a metallic gasket in which an area increased in thickness compared with the metallic sheet is provided at a zone between the recess and only the combustion hole of various holes. The thickened area is provided by at least any one of a bead formed on the metallic sheet, a folded construction formed by folding back a periphery of the combustion hole, a hollowed bulge containing therein a cavity, and a grommet fit over the periphery of the combustion hole. When the metallic gasket is squeezed, the sealing stress developed between the mating surfaces is allowed to increase at the thickened area and, therefore the compressive sealing stress rests on both the thickened area and the elastic sealing member.
With the metallic gasket constructed as stated earlier, the elastic sealing member may be free from an occurrence of flowage of the sealant even under either the squeezed condition or the operating condition that might cause any shrinkage and/or expansion in the clearance between the mating surfaces. Thus, the elastic sealing member may serve its useful function within the elastic characteristic range. This helps ensure the properly tight and enduring sealing condition, thereby keeping the gasket against premature degradation and any collapse. Accordingly, the present invention succeeds in the provision of the metallic gasket superior in sealing performance, with even simple and inexpensive.